PREVENTION OF SINTERING DURING ANNEALING PROCESS OF FePt NANOPARTICLES COATED WITH ZnO SHELL

Abstract

Monodispersed 4.1 nm FePt nanoparticles with narrow size distribution were successfully synthesized by the chemical polyol process with co-reduction of Fe (acac)3 and Pt (acac)2 in the presence of 1,2-hexadecanediol as a reducing agent. To achieve hard ferromagnetic behavior with L10 phase and face center tetragonal (fct) structure, high temperature annealing is performed. Annealing causes the surfactant surrounding particles to decompose and agglomeration of particles occurs. In the present work, chemically synthesized FePt nanoparticles were coated with nonmagnetic ZnO oxide shell to prevent them from sintering. Coercivity of FePt and FePt/ZnO nanoparticles increases from 5 kOe to 10 kOe and 1.8 kOe to 6 kOe respectively, with the increasing annealing temperatures from 650 to 750°C.